Proposals have already been made in the publication "Waveguide Communication System for Centralized Railway Traffic Control," by T. Kawakami et al, IEEE Trans. on Vehicular Communications, September 1964, pp. 1-18, to dispose a circular waveguide along the track of a high speed train, the waveguide being provided with directional couplers and with radiating auxiliary waveguides, and with the trains being provided with transmit and/or receive antennas. Such a system makes it possible to transmit data and telephone conversations and television pictures between the train and a control station. However, it requires relatively complex and expensive apparatus to be installed all along the track. It was only used experimentally along a length of track, and solely for transmitting data, and to this day has not given rise to industrial use. A system of the same nature described by H. M. Barlow, in "The Radio and Electronic Engineer", May 1967, pp. 275-281, using a different waveguide structure and likewise for the sole purpose of transmitting data, suffers from the same drawback of complexity and cost and has likewise not given rise to industrial exploitation.